Din 76-a Pdf -

Specifically, refers to the "normal design" of a thread undercut for external ISO metric threads. It is used when no other specific indications are provided on technical drawings or product standards.

The English translation is prepared by the DIN language service; however, the standard notes that “in case of doubt, the German‑language original shall be considered authoritative.”

: Provides a breakdown of run-outs and undercuts for metric threads.

A standard DIN 76-A undercut consists of three main geometric elements: Undercut Diameter (

According to the DIN 76-1 PDF , Form A represents the for external thread undercuts. It is the default choice for engineering drawings unless technical constraints (such as space limitations) require the shorter Form B. Specification for Form A (Normal) Application External ISO metric threads (coarse or fine). Undercut Width ( ) Typically calculated as (where is the thread pitch). Undercut Diameter ( )

DIN 76-1 is the standard established by the Deutsches Institut für Normung (German Institute for Standardization) that dictates the dimensions for for ISO metric threads. din 76-a pdf

If you are a student or hobbyist, a summary table from a textbook will suffice for learning. But if you are a professional engineer or a manufacturing shop, purchase the official DIN 76-1:2016-10 and DIN 76-2:1990-03 PDFs from Beuth Verlag. Consider it a small investment in quality and legal safety.

| Feature | Dimension | Value (mm) | | :--- | :--- | :--- | | Thread Pitch | P | 1.5 | | Run-out length (x) | Short | 3.0 | | Run-out length (x) | Long | 4.5 | | Undercut width (b) | ~ | 3.2 – 3.7 | | Undercut bottom dia (d₁) | ~ | 8.0 |

If you require the official, fully detailed engineering document for compliance or auditing purposes, you can obtain the official (which covers Form A external threads) directly through the Beuth Verlag website or the Deutsches Institut für Normung (DIN) portal. Many manufacturing and engineering software suites (like SolidWorks, Autodesk Inventor, and McMaster-Carr CAD libraries) also come pre-loaded with DIN 76-A configurations for automatic insertion into designs. If you are working on a specific design, let me know:

Ignoring DIN 76 leads to "stress risers"—tiny points where the metal is more likely to crack under load. By following the standard's undercut specs, you distribute the load evenly, making your assembly both safer and more reliable. DIN 76 Standards Overview | PDF - Scribd

I can provide the exact dimensions or help you choose the right tool specifications. Share public link Specifically, refers to the "normal design" of a

If you are currently setting up a manufacturing print or a CNC program, let me know:

To guarantee access to the most accurate and legally binding version of the standard, the official must be purchased from authorized distributors. This provides several critical benefits:

The dimensions of a DIN 76-A undercut are directly proportional to the pitch (

When a bolt or threaded shaft is manufactured, the threading tool (such as a die or single-point cutting tool) cannot cut a full, usable thread right up to a shoulder or a solid face. The geometry of the tool requires a exit path. Without a thread undercut:

: If you need a quick visual reference for hole diameters and metric coarse/fine threads, the Seco Tools Threading Poster is a staple for machine shops. Why It Matters for Design A standard DIN 76-A undercut consists of three

Standards are periodically revised. DIN 76-1:2025-10 is the current, most up‑to‑date version that supersedes all earlier editions, such as the 2016-08 version. The publication history shows multiple revisions in quick succession (2024-11, 2025-07, 2025-10). These rapid updates address editorial corrections and minor technical improvements. Always refer to the latest version to ensure your design uses current specifications.

The letter “A” refers to , which is the normal‑length thread undercut for external threads (bolts, screws, studs). Its shorter counterpart is Form B, which is used only when technical constraints require a shorter relief zone. Both forms are illustrated and dimensioned in the tables of DIN 76‑1.

For most professionals, the small purchase price is a worthwhile investment in and having the latest, correct version .

Standard thread undercut for internal (female) threads.